In the past, there has been known the method of control of an NC machine tool which outputs correction data corresponding to an amount of wear of a tool to a correction part of an NC device to correct a tool path (for example, see PLT 1). In the method described in this PLT 1, the cutting edge of the tool used is divided into several portions, then the spindle rotational speed, feed speed, and other machining conditions and the position command of the feed axis instructed by the processing program are used to cumulatively add the tool path length and cutting length of each portion which contacts the workpiece and find the amount of wear of each portion.
In this regard, when machining a workpiece, usually a tool is not used over its entire area. Only part is used. For this reason, even when part of a tool becomes worn and is unable to be used, sometimes portions of the tool remain which can still be used. From the viewpoint of effective utilization of a tool, it is preferable to use such portions which can still be used for machining a workpiece.
On this point, the method which is described in PLT 1 finds the amount of wear for each portion of a tool so as to correct the tool path, but no consideration is given to which portion of the tool can be utilized.
PLT 1: Japanese Patent No. 3099286